Temporal trends in phosphorus and lacustrine productivity in Lake Simcoe inferred from lake sediment

The historical phosphorus record and lake productivity of Lake Simcoe (southern Ontario, Canada) was reconstructed based on sediment cores collected throughout the lake. Sediment phosphorus concentrations have increased in all basins, in particular since the 1970s, with most changes occurring in the non-apatite (organic and inorganic) phosphorus fractions. Similarly, sediment organic carbon and nitrogen concentrations have increased significantly, molecular C:N and C:P ratios have decreased and delta C-13(org) delta N-15 have increased. These data suggest that autochthonous primary production has increased over the last four decades. The apparent contradiction with modeling efforts is reconciled if we consider that bioavailable phosphorus has made up an increasing proportion of the total phosphorus load over the last several decades. This study suggests that the forms of P delivered to Lake Simcoe must be considered for the development of a sound management plan. Crown Copyright (C) 2011 Published by Elsevier B.V. on behalf of International Association for Great Lakes Research. All rights reserved.